Steam cookers conventionally cook foods by the use of hot steam and may be powered by a steam generator which is either gas fired or electrically powered. Large steam cookers for commercial or restaurant food preparation typically comprise one or more large cooking compartments mounted on top of a base compartment containing a gas or electric steam generator, sometimes referred to as a "boiler". Typically, each compartment of a large steam cooker has dimensions sufficient to accept five or six trays, each tray having a depth of about 21/2 inches. Most typical steam cookers have two such cooking compartments, mounted one on top of the other, bringing the total capacity of the steam cooker to ten or twelve trays. In order to provide sufficient heating capacity to quickly and completely cook large amounts of food, a powerful steam generator is required. Conventional steam generators of this type are relatively bulky, and typically only one such steam generator will fit into a 24 inch wide base compartment typical of such steam cookers.
Although a single steam generator, typically having a heat output of about 240 kBTU/hr, is sufficient for a ten or twelve pan steam cooker, such steam generators have a number of disadvantages. Firstly, the steam generator consumes the same amount of fuel regardless of whether one or both of the compartments are being used, resulting in a considerable waste of fuel during times when the steam cooker is not being used to its full capacity. Secondly, steam generators of this type tend to be relatively inefficient, having an efficiency of about 50% based on the amount of heat produced from a given amount of fuel. In order to meet efficiency standards in some jurisdictions, it may be necessary for such steam generators to be outfitted with relatively expensive devices to recapture heat which would otherwise be wasted.
Other types of steam generators have been developed which are more compact and more efficient than the conventional steam generator described above. For example, U.S. Pat. No. 6,000,392 discloses a steam cooker in which one steam generator is provided for each cooking compartment, and in which the steam generators are sufficiently small to allow them to be arranged in side-by-side relation to the cooking compartments. This type of steam generator has an efficiency of about 70%, considerably higher than that of conventional steam generators, and generates a large amount of high quality steam in relation to its size. However, the heat output of this type of generator is limited, and therefore it is used primarily in smaller steam cookers in which one such generator supplies steam to a single compartment having a capacity of three pans.
Therefore, the need exists for a more compact, efficient steam generator for large capacity steam cookers.